Power efficient method for cold storage data retention management

• US 8,843,700 B1
• Filed: 11/29/2013
• Issued: 09/23/2014
• Est. Priority Date: 11/29/2013
• Status: Active Grant

• Current Assignee: NGD Systems, Inc.
• Original Assignee: NxGn Data, Inc.
• Inventors: Salessi, Nader, Alcantara, Joao
• Primary Examiner(s): TSAI, SHENG JEN
• Application Number:
  US14/093,335
• Time in Patent Office: 298 Days
• Field of Search: 711/103
• US Class Current: 711/103
• CPC Class Codes: G06F 1/3275 Power saving in memory, e.g. RAM, cache
• CPC Class Codes: G06F 11/1469 Backup restoration techniques
• CPC Class Codes: G06F 12/0246 in block erasable memory, e.g. flash memory
• CPC Class Codes: G06F 2212/1032 Reliability improvement, data loss prevention, degraded operation etc
• CPC Class Codes: G06F 2212/7205 Cleaning, compaction, garbage collection, erase control
• CPC Class Codes: G06F 3/0625 Power saving in storage systems
• CPC Class Codes: G06F 3/0634 by changing the state or mode of one or more devices
• CPC Class Codes: G06F 3/0655 Vertical data movement, i.e. input-output transfer; data movement between one or more hosts and one or more storage devices
• CPC Class Codes: G06F 3/0679 Non-volatile semiconductor memory device, e.g. flash memory, one time programmable memory [OTP]
• CPC Class Codes: G11C 16/349 Arrangements for evaluating degradation, retention or wearout, e.g. by counting erase cycles
• CPC Class Codes: Y02D 10/00 Energy efficient computing, e.g. low power processors, power management or thermal management

Abstract

A system and method for storing infrequently accessed data with reduced power consumption. In one embodiment, a solid state drive (SSD) includes flash memory and environmental data logging circuitry. The SSD is shut off or operated in a sleep mode to reduce power consumption, and turned on or transitioned to an active mode as needed when data on the SSD is to be accessed, or when a calculation, based on a number of erase cycles previously performed in the flash memory and on a temperature history of the SSD indicates that a data refresh may be needed to prevent data corruption in the SSD, due to data retention limitation of the nonvolatile memory in the SSD.

Claims

1. A method for operating a solid state drive (SSD) connected to a host, the SSD comprising nonvolatile memory and environmental data logging circuitry (EDLC) and a source of a battery power, the method comprising:

requesting, by the host, a length of a first time interval from the SSD;

providing, by the SSD, the length of the first time interval to the host;

discontinuing, by the host, during the first time interval, a primary power supplied to the SSD;

powering of the EDLC, by the SSD, from the source of the battery power during the first time interval;

logging, by the EDLC, of environmental data at a plurality of points in time;

restoring, by the host, of the primary power supplied to the SSD, at the end of the first time interval; and

refreshing of data stored in the SSD, by the SSD, when a module evaluated by the SSD indicates that, based on the logged environmental data, refreshing of the data is required.

2. The method of claim 1, wherein the environmental data comprises a temperature of the SSD.

3. The method of claim 2, wherein the environmental data comprises a time stamp.

4. The method of claim 1, comprising recording, by the SSD, a number of erase cycles performed on the nonvolatile memory.

5. The method of claim 1, wherein the providing, by the SSD, of the length of the first time interval to the host comprises executing a remaining data life module.

6. The method of claim 5, wherein the remaining data life module is configured to accept as inputs a temperature history of the SSD since a most recent refresh, and a number of erase cycles previously performed on the nonvolatile memory.

7. A method for operating a solid state drive (SSD) connected to a host, the SSD comprising nonvolatile memory, the host comprising an environmental data logging system, the method comprising:

requesting, by the host, a length of a first time interval from the SSD;

providing, by the SSD, the length of the first time interval to the host;

discontinuing, by the host, during the first time interval, a power supplied to the SSD;

logging, by the environmental data logging system, of environmental data at a plurality of points in time during the first interval;

restoring, by the host, of the power supplied to the SSD, at the end of the first time interval;

providing, by the host, logged environmental data to the SSD; and

refreshing of data stored in the SSD, by the SSD, when a module evaluated by the SSD indicates that, based on the logged environmental data, refreshing of the data is required.

8. The method of claim 7, wherein the environmental data comprises a temperature of the SSD.

9. The method of claim 8, wherein the environmental data comprises a time stamp.

10. The method of claim 7, comprising recording, by the SSD, a number of erase cycles performed on the nonvolatile memory.

11. The method of claim 7, wherein the providing, by the SSD, the length of the first time interval to the host comprises executing a remaining data life module.

12. The method of claim 11, wherein the remaining data life module is configured to accept as inputs a temperature history of the SSD since a most recent refresh, and a number of erase cycles previously performed on the nonvolatile memory.

13. A method for operating a solid state drive (SSD) connected to a host, the SSD comprising nonvolatile memory and environmental data logging circuitry (EDLC), the method comprising:

instructing, by the host, the SSD to transition to a sleep mode;

transitioning, by the SSD, to the sleep mode;

logging, by the EDLC, of environmental data at a plurality of points in time, while the SSD is in the sleep mode;

instructing, by the host, the SSD to transition to an active mode;

transitioning, by the SSD, to the active mode;

refreshing of data stored in the SSD, by the SSD, when a module evaluated by the SSD indicates that, based on the logged environmental data, refreshing of the data is required; and

sending, by the SSD, status information to the host, wherein the status information comprises a new sleep interval.

14. The method of claim 13, wherein the environmental data comprises a temperature of the SSD.

15. The method of claim 14, wherein the environmental data comprises a time stamp.

16. The method of claim 13, comprising recording, by the SSD, a number of erase cycles performed on the nonvolatile memory.

17. The method of claim 13, wherein the module evaluated by the SSD is configured to accept as inputs a temperature history of the SSD since a most recent refresh, and a number of erase cycles previously performed on the nonvolatile memory.